Prototype for the client supplied function that is called
whenever a port is registered or unregistered.
@param port the ID of the port
@param arg pointer to a client supplied data
@param register non-zero if the port is being registered,
zero if the port is being unregistered
Prototype for the client supplied function that is called whenever a port is registered or unregistered.
@param port the ID of the port @param arg pointer to a client supplied data @param register non-zero if the port is being registered, zero if the port is being unregistered